Abstract: To investigate the inhibitory effect of Taraxacum glycoprotein on lipopolysaccharide-induced (LPS-induced) inflammation in RAW264.7 cells and elucidate the underlying molecular mechanism, an in vitro model of inflammation in RAW264.7 macrophages stimulated by LPS was established. The proliferation of RAW264.7 cells were detected by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) method and the secretion of nitric oxide (NO) was detected by Griess reagent method. The inhibitory effect of Taraxacum glycoprotein on the mRNA expression of LPS-induced inflammatory cytokines such as tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and inducible nitric oxide synthase (iNOS) in RAW264.7 cells was examined using reverse transcription-polymerase chain reaction, and the effect of Taraxacum glycoprotein on the secretion levels of LPS-induced inflammatory cytokines such as TNF-α and IL-6 was detected by enzyme-linked immunosorbent assay as well as the effect on its upstream signaling proteins including P-IκB-α and IκB-α by Western blot. Results: Taraxacum glycoprotein could significantly inhibit the secretion of NO, the mRNA expression of IL-6, TNF-α and iNOS and the secretion of IL-6 and TNF-α (P < 0.05, P < 0.01, respectively). Taraxacum glycoprotein resulted in a significant up-regulation of IκB-α protein expression (P < 0.001) and a significant down-regulation of P-IκB-α in a concentration-dependent manner (P < 0.05). The percentage inhibition of TNF-α secretion was 28.6%, 65.4% and 89.3%, and the percentage inhibition of IL-6 secretion was 32.3%, 54.1% and 85.7%, respectively, at concentrations of 250, 500 and 1 000 μg/mL. Conclusion: The nuclear factor-kappa B signal transduction pathway is indirectly inhibited by dandelion glycoprotein, and it has a significant anti-inflammatory effect in vitro in a dose-dependent manner.

Key words: Taraxacum F.H.Wigg., glycoprotein, inflammatory factor, nuclear factor-kappa B